Mule is a work queue for CPU intensive tasks. You can use it to offload tasks
that would otherwise kill your fast, responsive event loop. It's a bit like
threads a gogo, except using processes not threads.

Mule works by using node's child_process.fork() method to pre-fork a bunch of
processes using a script you define. It sets up a task queue to which you can
push blocking tasks onto and listen for the result. As worker processes become
available they alert the work queue that they're ready to accept more work.
Tasks are sent and results received using node's inbuilt IPC for forked node
processes.

Imagine you have a node process which needs to stay responsive to web requests,
user input or whatever. However it has some heavy CPU intensive work to do
calculating fibonacci numbers. Here's how mule can help unburden your poor
server:

parent.js

var WorkQueue =require('mule').WorkQueue;

var workQueue =newWorkQueue(__dirname+'/worker.js');

// Generate a series of fibonacci numbers using the work queue to avoid blocking.

var waiting =100;

for(var i =1; i <=100; i++){

// Generate random number to calculate a fibonacci sequence on

var n =Math.floor(Math.random()*40)+1;

// Wrap in anonymous function so we still have access to i & n

(function(i, n){

workQueue.enqueue(n,function(result){

console.log(i +': fibo('+ n +') = '+ result);

if(--waiting ===0){

// All jobs are complete so we can safely exit

console.log('\nDone.')

process.exit(0);

}

});

})(i, n);

}

console.log('See, no blocking!');

And here's the worker:

worker.js

/**

* Calculate a Fibonacci number. Note that if you ran this in the main event